Republic XP-69

Apteryx

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Hi, all...

To remind my readers the backstory on the p-69, aka AP-18::

Republic Aircraft had a WWII fighter project to be powered by a single Wright Tornado engine mid-mounted, a la the Airacobra. It was a new project, and not a development of their P-47.

I've seen at least one 3-view of the above-named fighter project, in a compilation of "project" drawings put out by the AAHS called Scale-Master Fax File no. 7. I've attached a scan. My question: why do you think that a new design would feature a wing planform with a constant-span inboard section? There's no dihedral break; no constant width in the center to go with the constant span. You see what I'm saying here?

One could hypothesize that some overworked engineer just stuck that section in as an insert on the drawing to increase wing area to a specified amount, but one has a harder time believing the plane would have progressed to prototype status with that feature. But I may be missing something. Any thoughts?
 

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AFAIK, the XP-69 did not reach prototype status, mockup only, with a configuration different from the drawing shown.

Best regards,

Artie Bob
 
Mockup and early drawing here
 

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Artie Bob:

Sorry, I didn't mean to imply that sheetmetal was ever cut on a prototype. Just that the logic of the wing plan escapes me.

Justo: thank you so much--I'd not seen those images! The planform of the version built in mockup is very p-39-like.

The 3-view I posted was declared to be a projected production version, with a cut-down rear fuselage and all-round vision canopy. And weird wings.

PS--Rereading my first post, I was being generally incoherent. I meant constant chord center section, not constant span.
 
On a related note, does anyone have a picture of the Wright R-2160 Tornado engine?

Thanks
 
Four images of the preserved R-2160 Tornado at the Aviation Hall of Fame of New Jersey Museum (Teterboro, NJ).

http://www.fourfold.ca/billm/Aviation/AviationHallOfFameTeterboroNJ/AircraftEngines/pages/09WrightTornadoR2160.htm

Same collection: http://www.williammaloney.com/Aviation/AviationHallOfFameTeterboroNJ/AircraftEngines/index.htm
 
Apteryx said:
My question: why do you think that a new design would feature a wing planform with a constant-span inboard section? There's no dihedral break; no constant width in the center to go with the constant span. You see what I'm saying here?

One could hypothesize that some overworked engineer just stuck that section in as an insert on the drawing to increase wing area to a specified amount, but one has a harder time believing the plane would have progressed to prototype status with that feature. But I may be missing something. Any thoughts?

there was another US aircraft of the period which was a collage of several different other fighters to facilitate manufacturing (was it a Boeing? the name 'Eagle' comes to mind for some reason*). Anyway, it used P-40 wings IIRC, and had inserts to achieve the design span. Maybe there is something like that going on here

*did some research. it's the Fisher Eagle. The P-40 outer panels were later replaced with P-51 panels.
 
AeroFranz said:
there was another US aircraft of the period which was a collage of several different other fighters to facilitate manufacturing (was it a Boeing? the name 'Eagle' comes to mind for some reason*). Anyway, it used P-40 wings IIRC, and had inserts to achieve the design span. Maybe there is something like that going on here

There are several parallels between the P-69 and the Fisher P-75, but I think only the latter was a "Franken-fighter."

If the P-69 used somebody else's wings (and I can't tell whose those would be) they would have had to rework the whole main gear installation to have them where the drawing places them. Not a trivial undertaking!

It's just one of those mysteries--trivia, I suppose, but it will keep bugging me.
 
The XP-75 used an SBD fuselage, tail & wing center section, P-40 wings & F4U landing gear. The XP-75A was an 'improved' redesign of that airframe. One proposal was to use P-51 wings, but that never happened. I think the landing gear location was the P-40's.



Apteryx said:
AeroFranz said:
there was another US aircraft of the period which was a collage of several different other fighters to facilitate manufacturing (was it a Boeing? the name 'Eagle' comes to mind for some reason*). Anyway, it used P-40 wings IIRC, and had inserts to achieve the design span. Maybe there is something like that going on here

There are several parallels between the P-69 and the Fisher P-75, but I think only the latter was a "Franken-fighter."

If the P-69 used somebody else's wings (and I can't tell whose those would be) they would have had to rework the whole main gear installation to have them where the drawing places them. Not a trivial undertaking!

It's just one of those mysteries--trivia, I suppose, but it will keep bugging me.
 
For more about the Tornado engine and some drawings go to:

http://www.weakforcepress.com/tornado_2.htm
 
Does anyone have info and images re Republic XP-69.
 

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How's this, Steve? ;)

http://www.weakforcepress.com/tornado_2.htm

http://home.att.net/~jbaugher1/p69.html

http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=2270

http://www.anigrand.com/AA2069_XP-69.htm

Moonbat

PS- Just to give you a friendly heads-up, I think the mods might relocate this topic to EARLY PROJECTS.
 

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Also, when a radial and a liquid-cooled engine do the same.

Definitely check out Kimble McCutcheon's book on the Wright R-2160 for (extensive) details.
 
Some additional info-Post-1
 

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Some additional info-Post-2
 

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Some additional info-Post-3
 

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well, if i am not on mistake there was two proposed version of armament : or one cannon of 37 mm and two gun of 12,7 mm on each wing or classic three gun of 12,7 mm on each wing ! ::)
 
Having seen pictures of Wrights 42 cylinder Tornado (offhand I can't recall if the engine is on display at Wright Patterson or not) along with skeleton cad drawings I have always wondered what the 70 cylinder version of the engine would of sounded like
 
A radial doesn't 'have to be' air cooled.

GeorgeA said:
Also, when a radial and a liquid-cooled engine do the same.

Definitely check out Kimble McCutcheon's book on the Wright R-2160 for (extensive) details.
 
Justo - I just wonder how are you organazing million files named "EscanearXYZ.jpg" :)
 
Yes, essentially Wright designed a 14-cylinder liquid-cooled radial and combined three units to make the 42-cylinder R-2160. A 70-cylinder (five 14-cyl) was contemplated, but in such long, multi-cylinder configurations, the weight of the crankshaft, the intake charge distribution, and cylinder head complexity become the limiting factors. Add in exhaust routing for the turbocharger and it gets really difficult.

Interestingly, Wright's later work on the stratified charge rotary included an eight-rotor design, with each rotor displacing 580 cubic inches.
 
GeorgeA said:
Yes, essentially Wright designed a 14-cylinder liquid-cooled radial and combined three units to make the 42-cylinder R-2160. A 70-cylinder (five 14-cyl) was contemplated, but in such long, multi-cylinder configurations, the weight of the crankshaft, the intake charge distribution, and cylinder head complexity become the limiting factors. Add in exhaust routing for the turbocharger and it gets really difficult.

Interestingly, Wright's later work on the stratified charge rotary included an eight-rotor design, with each rotor displacing 580 cubic inches.

From the drawings I have seen the 14 cylinder two row sections each had their own crank shaft. The engine sections (think of the Tornado as a compound engine like the big Allison) would be connected together by lay shafts that ran in the Vee's between each bank of cylinders. Really I still don't think it as strange as the 18 cylinder engine in the Bugatti Veyron
 
Please see Bugatti T67 V16 from http://www.secretprojects.co.uk/forum/index.php/topic,1100.45.html
 

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While the 16 cylinder Bugatti aircraft engine is a little on the different side I meant the one in the car that IMO is Ferdinand Piesch's (sp) wet dream
 

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CAO 700 said:
The Anigrand kit looks really great!
Yes, I covet the kit. The nagging question I have about this version of the XP-69, and yes, I've raised it before, is: what is with the constant-chord center section on the wing? It appears in some drawings of the plane, but not anything I've seen that's contemporary with its development. And what sense does it make? It's constant-chord but not constant thickness. Nor is there a dihedral break, with a horizontal center-section, as in the T-6 Texan or the XP-75.

I just got a copy of Tornado: Wright Aero's Last Liquid-cooled Piston Engine. It's a wonderful reference, and I hope the author can fulfill his stated intention of writing a series of books on experimental engines. It has this nugget re the XP-69:
"One interesting finding of the full-scale tunnel testing...was that the aileron forces were too high. Several solutions were proposed, including an internal sealed balance with wedge trailing edge."

I never heard of a "wedge trailing edge" but maybe that's the origin of the kink in the trailing edge? Doesn't explain the kinked leading edge, though.
 
No less than 57 pictures on NASA's CRgis website from the 3/4 scale model wind tunnel tests:

http://crgis.ndc.nasa.gov/historic/Test_139:_XP-69_3/4%E2%80%93scale_Model_%28Stability_and_Cooling%29

800px-LMAL_29688.JPG
 
Apteryx said:
Republic Aircraft had a WWII fighter project to be powered by a single Wright Tornado engine mid-mounted, a la the Airacobra. It was a new project, and not a development of their P-47.

In 2001 I published a book on the Wright Tornado aircraft engine that included a section on the Republic XP-69, one of the aircraft that was intended to use the engine. Please see
http://www.weakforcepress.com/

At that time my book contained the most complete information that had been published on the XP-69. In 2001 available sources all agreed that the XP-69 was a mid-engine fighter with the propeller driven via an extension shaft.

I have since discovered a drawing of the XP-69 at the U.S. National Archives that clearly shows a conventional tractor engine installation. This is the only drawing of Republic design AP-18 that I have ever seen. Please see
http://www.weakforcepress.com/XP-69/index.html and
http://www.weakforcepress.com/tornado_errata.htm


I apologize for the poor quality; the drawing was too large to duplicate with any of the equipment available at NARA, so I was forced to hang drawing and photograph it in sections.

The drawings clearly show the engine in front of the pilot and the space behind the pilot filled with the ducts, radiators, intercoolers, etc. required for a liquid-cooled turbosupercharged engine installation.

The unfortunate thing is that I discovered this drawing AFTER I had published my book on the Wright Tornado. In retrospect, I DID have details of the ducting and heat exchangers behind the pilot and should have realized while writing the book that there was no room for the engine behind the pilot.

The Republic AP-18 design is thought to be an evolution of the AP-12 design, which DID have a mid-mounted engine. It appears historians may have incorrectly assumed the AP-18 was a mid-engine aircraft also.
 
Very interesting, Kimble.

Thank you very much for sharing. The XP-69 is a pet might-have-been aircraft of mine, and these documents shed valuable new light on the subject.

Any idea if Republic ever planned a popular name for it (like Thunder-something)?
 

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